1. Field of the Disclosure
The present disclosure relates to a liquid crystal display (LCD) device, and more particularly, to an array substrate for a transflective liquid crystal display device and a method of fabricating the same.
2. Discussion of the Related Art
With rapid development of information technologies, display devices for displaying the information have been actively proposed and developed. More particularly, flat panel display (FPD) devices having a thin profile, light weight and low power consumption have been actively pursued. FPD devices can be classified into an emissive type and a non-emissive type depending on their light emission capability. In an emissive type FPD device, an image is displayed using light that emanates from the FPD device. In a non-emissive type FPD device, an image is displayed using light from an external source that reflects and/or transmits through the FPD. For example, a plasma display panel (PDP) device and a field emission display (FED) device are an emissive type. In another example, an electroluminescent display (ELD) device is an emissive type FPD device. Unlike a PDP and an ELD, a liquid crystal display (LCD) device is a non-emissive type FPD device that uses a backlight as a light source.
Among the various types of FPD devices, liquid crystal display (LCD) devices have been widely used as monitors for notebook computers and desktop computers because of their high resolution, color rendering capability and superiority in displaying moving images. The LCD device displays images by controlling a transmittance of light through the device. More particularly, liquid crystal molecules of a liquid crystal interposed between two substrates facing each other control light transmission in response to an electric field generated between electrodes on the substrates.
Because the LCD device does not emit light, the LCD device needs a separate light source. Thus, a backlight is disposed on the rear surface on a liquid crystal panel of the LCD device, and images are displayed with the light emitted from the backlight and transmitted through the liquid crystal panel. Accordingly, the above-mentioned LCD device is referred to as a transmission type LCD device. The transmission type LCD device can display bright images in a dark environment due to the use of a separate light source, such as a backlight, but may result in large power consumption because of the use of the backlight.
To solve the problem of the large power consumption, a reflection type LCD device has been developed. The reflection type LCD device controls a transmittance of light by reflecting the outside natural light or artificial light through a liquid crystal layer. In a reflection type LCD device, a pixel electrode on a lower substrate is formed of a conductive material having a relatively high reflectivity and a common electrode on an upper substrate is formed of a transparent conductive material. Although the reflection type LCD device may have lower power consumption than the transmission type LCD device, it may have low brightness when the outside light is insufficient or weak.
To solve both the problems of the large power consumption and the low brightness, a transflective LCD device combining the capabilities of a transmission type LCD device and reflection type LCD device has been suggested. The transflective LCD device can select a transmission mode using a backlight while in an indoor environment or a circumstance having no external light source, and a reflection mode using an external light source in an environment where the external light source exists.
FIG. 1 is a plan view of an array substrate for a transflective LCD device according to the related art. In FIG. 1, a gate line 5 and a data line 30 are formed to cross each other and define a pixel region P. A common line 6 is formed across the pixel region P and parallel to the gate line 5. The pixel region P is divided into a reflective area RA and a transmissive area TA by the common line 6.
A thin film transistor Tr is formed in the pixel region P as a switching element and is connected to the gate line 5 and the data line 30. The thin film transistor Tr includes a gate electrode 8, a gate insulating layer (not shown), a semiconductor layer 20, and source and drain electrodes 33 and 36. The source and drain electrodes 33 and 36 are spaced apart from each other. A pixel electrode 62 is formed in the pixel region P and contacts the drain electrode 36 of the thin film transistor Tr. The pixel electrode 62 has substantially a plate shape and includes bar-shaped first openings op1 and second openings op2 in the transmissive area TA and the reflective area RA, respectively. The bar-shaped first openings op1 and second openings op2 are formed along different directions, that is, the first and second openings op1 and op2 have different length directions, which are directions of their lengths longer than widths. More particularly, the first openings op1 in the transmissive area TA are formed parallel to the data line 30, and the second openings op2 in the reflective area RA are formed aslant at a predetermined angle with respect to the data line 30. The pixel electrode 62 in the pixel region P is separated from a pixel electrode in a next pixel region.
Although not shown in the figure, a common electrode is formed in the pixel region P, and the common electrode has a size corresponding to the pixel region P. The common electrode in the pixel region P is connected to a common electrode in a next pixel region, and the common electrodes are electrically connected to each other all over the array substrate 1. An insulating layer (not shown) is formed between the common electrode and the pixel electrode 62. Therefore, a fringe electric field is induced between the common electrode and the pixel electrode 62 spaced apart from each other with the insulating layer interposed therebetween.
Further, a reflective layer (not shown) is formed in the reflective area RA so that the device operates as a reflection mode. The reflective layer is formed of a metallic material having relatively high reflectivity.
In the transflective LCD device including the array substrate 1, there occurs disclination adjacent to the data line 30 in the reflective area RA, and relatively dark portions are irregularly shown. This causes non-uniform brightness, and thus image qualities are lowered. The disclination is caused by liquid crystal molecules arranged disorderly, and the disclination mainly occurs around ends of the first and second openings op1 and op2 for inducing the fringe electric field.
Moreover, in the array substrate 1, since the ends of the second openings op2 in the reflective area RA are disposed in the pixel region P, the disclination seriously occurs, as shown in FIG. 2, which shows a simulating result about the reflective area of the pixel region according to the related art. To prevent the lowering of the image qualities due to the disclination, a black matrix on a color filter substrate opposite to the array substrate 1 should have a widened width to cover the data line 30 and the portions where the disclination occurs. Therefore, the aperture ratio is decreased.
The pixel electrode 62 receives signal voltages, which vary at any time, from the data line 30. Therefore, it is desirable that the pixel electrode 62 does not overlap the data line 30, and the ends of the second openings op2 are spaced apart from the data line 30. Accordingly, in the array substrate 1, it is hard to prevent the lowering of the image qualities without the decrease of the aperture ratio in the reflective area RA.